From: Robert Klemme <bob.news@...>
Date: 2005-03-24T05:39:53+09:00
Subject: Re: Iterating through a string and removing leading characters


"Randy Kramer" <rhkramer@gmail.com> schrieb im Newsbeitrag 
news:200503231224.46149.rhkramer@gmail.com...
> On Wednesday 23 March 2005 10:29 am, Florian Gross wrote:
>> Randy Kramer wrote:
>> > Aside: but:
>> >
>> > irb(main):005:0> 10.times { puts s1[2].id }
>> > 211 [times ten]
>> > => 10
>> > irb(main):006:0>
>> >
>> > Which (maybe) looks nicer/more reasonable, except I don't know why the 
>> > 3
>> > digit ID in this case.
>>
>> string[number] returns either nil or the ASCII number of the character
>> at that place.
>
> Thanks, but I'm still confused--s1 is "This is a test", so 211 is neither 
> nil
> nor ASCII for "i", and besides, I asked for the (object_)id.
>
> 211 does happen to be 2*?i+1--maybe there's a clue there? (and the same 
> thing
> holds for the previous character (h) which shows up as 209)

I think there is a relation between object ids and values for Fixnums but 
I'm not sure.  It's also quite unimportant IMHO.  But it seems to be exactly 
the relationship you assumed:

>> 20.times {|ch| printf "%02x %02x %02x\n", ch, ch.id, (ch<<1)+1}
00 01 01
01 03 03
02 05 05
03 07 07
04 09 09
05 0b 0b
06 0d 0d
07 0f 0f
08 11 11
09 13 13
0a 15 15
0b 17 17
0c 19 19
0d 1b 1b
0e 1d 1d
0f 1f 1f
10 21 21
11 23 23
12 25 25
13 27 27
=> 20

> My original concern: I was hoping that s1[0] and similar did not create 
> new
> objects, and I suspect they don't, but I'm not sure.

They don't because Fixnums are treated specially for performance reasons.

>> s = "This is a test"
=> "This is a test"
>> 10.times {c=s[2]; p [c, c.chr, c.id]}
[105, "i", 211]
[105, "i", 211]
[105, "i", 211]
[105, "i", 211]
[105, "i", 211]
[105, "i", 211]
[105, "i", 211]
[105, "i", 211]
[105, "i", 211]
[105, "i", 211]
=> 10

Regards

    robert